1. Field of the Invention
The present invention relates, according to the preamble of Claim 1, to a device for a drilling and/or percussive hammer having a tool receptacle for holding a tool and transferring a torque to the tool.
2. Description of the Related Art
Such a device is known e.g. under the trade name “SDS-max,” and has proven successful in practice.
A device of this sort is described in DE 37 16 915 A1. According to this patent, a percussive drilling tool has at least two grooves that open out at the end of the tool shaft, in which web-shaped dogs of a tool receptacle of the drilling hammer can engage. In addition, two recesses are provided in the tool shaft that are closed at both sides and that are situated diametrally opposite one another, in which locking elements provided on the tool shaft can engage.
The design of such a known “SDS-max” device is explained in more detail below on the basis of FIG. 1. FIG. 1 shows a sectional view of the front, tool-receiving end of a known drilling and/or percussive hammer.
In the upper half of FIG. 1, a known pneumatic spring hammer mechanism is shown in the impact position, while the lower half of FIG. 1 shows the pneumatic spring hammer mechanism in the idle position.
A component of the pneumatic spring hammer mechanism is a hollow impact piston 1, which can be set into back-and-forth motion by a drive piston (not shown) in a known manner.
On its front end, impact piston 1 strikes a header 2 that is likewise capable of axial motion, and this header in turn transmits the impact action at its opposite end to the end surface of an insertion end (not shown) of a tool (e.g., of a drill or of a chisel).
The insertion end of the tool is capable of being introduced via an introduction opening 3 into an essentially hollow cylindrical recess that forms a tool holder 4. At the end of tool holder 4 situated opposite introduction opening 3, a fictitiously defined impact opening 5 is provided through which the impact effect of header 2 can be applied to the insertion end.
Tool holder 4 is a component of a tool receptacle 6 having three web-shaped rotational drivers 7 formed on the inside of tool holder 4. Rotational drivers 7 can be inserted into rotational driver grooves (not shown) in the insertion end of the tool, as is described for example in DE 37 16 915 A1. Another rotational driver is situated opposite the two rotational drivers 7 shown in FIG. 1.
In addition, tool receptacle 6 has two locking elements 8 that are capable of axial movement in through-holes 9 of tool holder 4, and—under particular circumstances explained below—are capable of radial movement.
With the aid of a spring-loaded plate 10, locking elements 8 are fixed axially against a guide 11, so that they cannot deviate radially outwards. In this position, they are held in assigned locking recesses (not shown) in the insertion end of the tool. The locking recesses in the tool are closed on both sides in the axial direction in the tool shaft, so that locking elements 8 can prevent a tool insertion end from being withdrawn from tool holder 4.
However, the operator can move a locking sleeve 12 together with plate 10 against the action of a spring 13 (to the right in FIG. 1), whereby locking elements 8 in through-holes 9 are also moved to the right. This causes locking elements 8 to slide out of their guide 11, so that they can move radially outwards. In this way, locking elements 8 move out of their assigned locking recesses, so that the insertion end becomes capable of moving freely in the axial direction and can be withdrawn from tool holder 4.
As presented, this principle of operation is known, so that a more detailed description is not necessary.
Although tools having the brand designation “SDS-max” have developed into a kind of standard, so that the shape and execution of the insertion ends of the tools cannot be further modified to any great extent, improvements are still possible in the tool receptacle.
Thus, e.g. for the axial supporting of the insertion end, and in order to seal the pneumatic spring hammer mechanism against the entry of foreign bodies into the hammer mechanism area, a header 2 is always required that transmits the impact action from impact piston 1 to the insertion end. The resulting space requirement is relatively large, and limits the design possibilities for impact piston 1. For example, it is not easy to modify the geometry of impact piston 1 in a manner that would be desirable in order to achieve a higher impact energy. In particular in hammers having a high impact power, or a large torque that is to be transmitted, there is the danger that the insertion ends—i.e., above all the rotational driver grooves in the insertion ends—will be knocked out relatively quickly, which can result in a shortened lifespan of the tools. From GB-A-1505907, a drilling or percussive hammer is known that has a tool receptacle for holding a tool and for transmitting a torque to the tool. The tool receptacle has on its inside a locking element with which a tool end is held in the tool holder and the drive torque is transmitted to the tool end.